Flexible plastic bags are widely used for a variety of purposes such as storing food items, either temporarily as in the case of packaging snacks or long term as in the case of freezer storage. Plastic bags of this style typically include flexible sidewalls made from, for example, polyethylene, that define an opening and an internal volume accessible through the opening. To seal the bag, interlocking closure strips may be provided about the rim of the opening.
One common problem which occurs with such bags is that, after the opening has been sealed, latent air may remain trapped in the internal volume. In addition to undesirably increasing the overall size of the sealed bag, the trapped air can cause spoilation of food items stored in the internal volume. Therefore, to remedy this problem, it is known to provide a one-way valve element attached to a flexible sidewall and communicating with the internal volume. The one-way valve element allows for the evacuation of the trapped air from the internal volume while also preventing the ingress of air from the surrounding environment into the internal volume. The one-way valve element may be activated in various ways such as, for example, by applying compressive pressure to the flexible sidewalls to force air from the internal volume or by engaging a nozzle of a vacuum source to the one-way valve element to draw air from the internal volume. An example of a one-way valve element that operates in conjunction with a vacuum source is provided in U.S. Pat. No. 6,581,641, issued to Skeens et al. and assigned to Illinois Tool Works Inc.
A problem that may arise with such bags that include one-way valve elements is that the flexible sidewall opposing the valve element and the sidewall to which the valve element is attached can actually clog the valve element preventing further evacuation. For example, it will be appreciated that placing the opposing sidewall against a solid surface and pressing the sidewall with the attached valve element toward the surface evacuates the internal volume by collapsing the sidewalls together. This also necessarily brings the opposing sidewall into contact with the valve element which can result in clogging. Likewise, where a vacuum source is used to evacuate the flexible bag, the opposing sidewall may be drawn under vacuum pressure into the valve element. A related problem is that collapsing the opposing sidewalls themselves together may trap air in other portions of the internal volume. These and other problems are remedied by the invention described herein.